CCD-RSM optimization of biodiesel production from waste cooking oil using Angulyagra oxytropis and Bellamya crassa snail shell-based heterogeneous catalysts

In the present study, labuk tharoi (Angulyagra oxytropis), and ningkhabi tharoi (Bellamya crassa) were utilized to produce CaO catalyst for biodiesel production using waste cooking oil (WCO). The snail shells were calcined at a temperature of 800-1000 degrees C for 4 h and characterized using XRD, FTIR, BET, SEM, and EDX analysis. Central composite design-response surface methodology (CCD-RSM) was employed, and the input parameters considered for optimization were (i) catalyst calcination temperature (800-1000 degrees C), (ii) methanol: oil ratio (molar) (6:1-12:1), (iii) catalyst loading (3-7 wt.%), and (iv) reaction temperature (55-75 degrees C). A quadratic regression model was aliased by CCD-RSM with R2 values of 0.9291 and 0.976 for waste cooking oil methyl ester-labuk tharoi (WCOME-LT), and waste cooking oil methyl ester-ningkhabi tharoi (WCOME-NT) models indicating a good fit. An optimum biodiesel yield of (95.87, 95.91 %) was obtained at catalyst calcination temperature (891, 886 degrees C), methanol to oil molar ratio (9.89:1, 9.67:1), catalyst loading weight % (7, 7 wt.%), and reaction temperature (75, 75 degrees C) for WCOME-LT and WCOME-NT model respectively. The calcination temperature has a major impact on the biodiesel yield as per analysis of variance. The catalyst reusability was up to four cycles with a biodiesel yield of more than 83 %.